Rapidly-dissolving halogenated hydantoin powders having improved flow, reduced dust, improved wetability, and increased bulk densities

ABSTRACT

A powdered halogenated hydantoin product having the following size distribution: (a) 70-100% halogenated hydantoin particles sized between 80 mesh and 200 mesh; (b) 0-20% particles sized larger than 80 mesh; and (c) 0-10% particles sized smaller than 200 mesh. The powdered product has superior dissolution and flow characteristics, while avoiding dusting where the product is used. Bromochlorodimethylhydantoin is the preferred halogenated hydantoin.

FIELD OF THE INVENTION

[0001] The present invention relates generally to halogenatedhydantoins, and more particularly to rapidly dissolving halogenatedhydantoin powders (particularly BCDMH powder) with improved flow,decreased dust, improved wetability, and increased density.

BACKGROUND OF THE INVENTION

[0002] One of the most pervasive problems in the paper making industryis the growth of biological organisms that interfere with themanufacturing process or negatively impact the quality of the finishedpaper. These organisms typically form into slimes on the machines, whichcan then become incorporated into the paper. Slimes in paper can affectpaper quality, and accordingly may affect the profitability of the mill.Slimes in the paper can also lead to “slime tears” during thepapermaking process, which may require the machine to be shut down andrestarted. Shut downs also can have a large effect on the profitabilityof the mill, due to the high capital cost associated with papermaking.Additionally, slimes in the paper may also cause unwanted tastes andodors, again affecting paper quality and mill profitability.

[0003] Historically, paper mills have used chemical treatments inconjunction with periodic shut downs to control biological fouling. Mostcommonly, chlorine or non-oxidizing biocides have been used in thosetreatments. Unfortunately though, chlorine presents handling anddischarge problems, while non-oxidizing biocides often have limitedefficacy and can be very expensive.

[0004] The halogenated hydantoin bromochlorodimethylhydantoin (“BCDMH”)has been used successfully in the cooling water and process industriesbecause of its generally good handling and discharge characteristics, aswell as its superior efficacy. Some problems remain, however, that limitthe utility of BCDMH in paper mills. For example, the trend in the paperindustry is to “close” mills, which means more water is recycled, lessfresh water is used, and less wastewater is discharged. This means thatless fresh water is available in the mill for various uses, and the millis more sensitive to the addition of fresh water because of water andchemistry balances. Because the most common forms of BCDMH—tablets andgranules—require large amounts of relatively clean water to dissolve,their use is limited in the paper manufacturing process.

[0005] As an alternative to tablets and granules, BCDMH powder has beenavailable for several years. It provides the advantage of a “quickdissolving” product in markets where this is critical because of thelimited availability of fresh water. However, several other issuesremain, particularly regarding flowability, dusting, wetability, andbulk density. From the flowability standpoint, powdered BCDMH frequentlyexhibits variable rates of flow, leading to inconsistent amounts offeed. From the dusting standpoint, the product has been very dusty,making it inconvenient to handle and sometimes requiring the use ofrespirators or other air purification systems. From the wetabilitystandpoint, the product, because of a portion of its small particlesize, expresses difficulty in wetting, and tends to float on the surfacein the mixing tank, rather than forming a suspension. From the densitystandpoint, the product is fluffy and light in appearance and weight,which requires larger and more costly packaging.

[0006] A need therefore exists for new powdered halogenated hydantoinproducts that meets the requirements for improved flow, reduced dust,improved wetability, and increased density. The present inventionaddresses that need.

SUMMARY OF THE INVENTION

[0007] Briefly describing one aspect of the present invention, powderedhalogenated hydantoin products such as BCDMH are prepared to provide thefollowing particle size distribution: (a) 70-100% halogenated hydantoinparticles sized between 80 mesh and 200 mesh; (b) 0-20% particles sizedlarger than 80 mesh; and (c) 0-10% particles sized smaller than 200mesh. These powdered products have superior dissolution and flowcharacteristics, with reduced dusting, improved wetability, andincreased density when compared to prior art products.

[0008] In another aspect of the present invention the powderedhalogenated hydantoin products are prepared to provide the followingparticle size distribution: (a) 90-100% halogenated hydantoin particlessized between 60 mesh and 200 mesh; (b) 0-5% particles sized larger than60 mesh; and (c) 0-5% particles sized smaller than 200 mesh.

[0009] One object of the present invention is to provide BCDMHcompositions having improved flowability, reduced dusting, improvedwetability, and increased density.

[0010] Other objects and advantages will be apparent from the followingdescription of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a graph showing dissolution rates for the currentinvention and Powder XG at 25° C.

[0012]FIG. 2 is a chart showing dissolution times at 90% for the currentinvention and Powder XG at 25° C.

[0013]FIG. 3 is a graph showing dissolution rates for the currentinvention and Powder XG at 35° C.

[0014]FIG. 4 is a chart showing dissolution times at 90% for the currentinvention and Powder XG at 35° C.

[0015]FIG. 5 shows the current invention as it feeds into the mixingchamber.

[0016]FIG. 6 shows the Powder XG as it feeds into the mixing chamber.

[0017]FIG. 7 shows a competitor's product as it is fed into the mixingchamber.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] For the purpose of promoting an understanding of the principlesof the invention, reference will now be made to preferred embodimentsand specific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the preferred embodiments, and such furtherapplications of the principles of the invention as described hereinbeing contemplated as would normally occur to one skilled in the art towhich the invention pertains.

[0019] As briefly described above, one aspect of the present inventionprovides powdered halogenated hydantoin compositions having improvedflowability, reduced dusting, improved wetability, and increaseddensity, while maintaining satisfactory dissolution rates. Thesepowdered products are particularly useful for treating water in papermills and other industrial applications, including, but not limited to,cooling water, breweries, food applications, and other process waters.

[0020] The inventive halogenated hydantoin powders have a specificparticle size distribution. In general, the particles are small enoughto provide rapid dissolution in water or other aqueous solutions, yetlarge enough to provide reduced dustiness and consistent, reliable flow.It has been found that the following particle size distribution providesthose characteristics:

[0021] (a) 70-100% particles sized between 80 mesh and 200 mesh;

[0022] (b) 0-20% particles sized larger than 80 mesh; and

[0023] (c) 0-10% particles sized smaller than 200 mesh.

[0024] More preferably, the halogenated hydantoin powders of the presentinvention have the following particle size distribution:

[0025] (a) 90-100% particles sized between 60 mesh and 200 mesh;

[0026] (b) 0-5% particles sized larger than 60 mesh; and

[0027] (c) 0-5% particles sized smaller than 200 mesh.

[0028] As indicated above, the inventive powders comprise any of thehalogenated hydantoins, including any or all of the mono- ordi-halogenated hydantoins. Most preferably, the powders comprise asubstantial amount of bromochlorodimethylhydantoin, with powderscomprising 20-70% BCDMH being most preferred. The remainder of thehalogenated hydantoin powder preferably includes other mono- ordi-halogenated dialkylhydantoins, such as chlorobromodimethylhydantoin,dibromodimethylhydantoin, dichlorodimethylhydantoin,dichloromethylethylhydantoin, etc.

[0029] The halogenated hydantoins used to make the inventive powders aremade by conventional methods, as is known to the art. A slurry istypically produced, and is then dried (e.g., by centrifuging and/orflash drying). The small (typically five- to ten-micron sized) particlesthus produced are compacted/agglomerated to increase their particlesize, using conventional compaction or agglomeration techniques.

[0030] The material is then screened to separate out the particles thatare too large or too small. The larger particles can then be reduced insize using a ball mill, hammer mill, air mill, etc. Smaller particlescan be returned to the compaction/agglomeration step.

[0031] It is to be appreciated that standard production processes make apowder that consists essentially of the desired halogenated hydantoin,but that up to about 15% salt and other minor by-products are normallyalso included in the mixture. For the purposes of this disclosure, thehalogenated hydantoin powders are described with respect to theirhalogenated hydantoin component only, it being recognized that otherproduction by-products are necessarily present in relatively minoramounts. Accordingly, a powder that consists essentially of halogenatedhydantoin particles is a powder that consists essentially of halogenatedhydantoin and the relatively minor amounts of salt and other by-productsthat would naturally occur with standard production processes.

[0032] The halogenated hydantoin powders of the present inventionprovide acceptable flow characteristics for use in the paper industry,as will be shown by the example(s) below. Under-feed of product isavoided, as is the build up of biological fouling with all itsassociated problems. Over-feed of product is also avoided, as are hightreatment costs and the potential for corrosion of the paper machine.

[0033] The halogenated hydantoin powders of the present invention alsoprovide acceptable “dusting” characteristics, as will be shown below.While dusting is a complex phenomenon that is not fully understood, itis known that small particle size materials tend to be more dusty, andthe addition of “work” (e.g, from granule compactors in the productionprocess) can also make material dustier. This may be related toelectrostatic charge on individual particles. The inventive powdersreduce dusting by reducing the amount of smaller particles andincreasing the amount of larger particles.

[0034] In particular, the inventive powders have a measured dust levelof no more than about 0.4% (when measured as described in Example 4below), with dust levels of less than about 0.2% being more preferred,and dust levels of less than about 0.1% being most preferred.

[0035] The halogenated hydantoin powders of the present invention alsoprovide acceptable “wetability” characteristics, as will be shown below.Wetability is an important factor in preparing a suspension (or slurry)of product to be pumped to specific treatment sites. Specializedequipment must be used to feed this product due to the corrosivity andcohesiveness of the product. The product is feed by a screw auger into amixing tank while adding water at a specific rate. The inventive processwill insure that a homogeneous mixture is maintained within the mixingtank and that no material will remain floating on the surface of thetank. An additional problem with low wetability products is the tendencyfor material to build up in and around the aforementioned slurry tank.This material must be cleaned by hand thus causing potential workerexposure and is also aesthetically objectionable to personnel.

[0036] The halogenated hydantoin powders of the present invention alsoprovide acceptable product densities. Since specialized packaging mustbe employed to transport and store the material, a higher, moreconsistent product density will reduce overall production costs as willbe shown below.

[0037] Finally, the halogenated hydantoin powders of the presentinvention also provide acceptable dissolution characteristics for use inindustry. Because the throughput of water in a water system can be asshort as several minutes, the halogenated hydantoin material must gointo solution rapidly. Because dissolution rate is directly proportionalto the surface area of the particles, rapid dissolution is best achievedwith small particles. Surprisingly it has been found that even thoughthe inventive powders are made of particles that are large enough tohave superior flow, reduced dust, improved wetability, and increaseddensity, they are still small enough to provide rapid dissolution.

[0038] In the preferred embodiments the inventive powders dissolve at arate such that at least 80% of the material is dissolved in ambienttemperature water in less than twelve (12) minutes, when measured asdescribed in Example 2. The more preferred embodiments providedissolution rates of 80% in less than ten (10) minutes, while the mostpreferred embodiments provide dissolution rates of 90% in less than nine(9) minutes.

[0039] In the preferred embodiments the inventive powders dissolve at arate such that at least 80% of the material is dissolved in 35° C. waterin less than ten (10) minutes, when measured as described in Example 3.The more preferred embodiments provide dissolution rates of 80% in lessthan eight (8) minutes, while the most preferred embodiments providedissolution rates of 90% in less than six (6) minutes.

[0040] The powders of the present invention find particular utility inthe paper industry, although other applications (e.g., cooling watertreatment, waste water treatment, etc.) may also be developed. Ingeneral, the powders are particularly useful when there is a need for aproduct that is easy to feed (i.e., flows consistently without dusting)and has rapid dissolution, or is required in large quantities.

[0041] In all of the anticipated applications, the powders are appliedby contacting the water to be treated with a sufficient amount of thepowder(s). Feeders, etc., may be used to facilitate delivering thepowder to the water. The amount of powder necessary to effect adequatewater treatment depends on the nature of the water being treated, and onthe requirements for treatment efficacy, as is known to the art.

[0042] Reference will now be made to specific examples illustrating thepreferred embodiments. It is to be understood that the examples areprovided to more completely describe preferred embodiments, and that nolimitation to the scope of the invention is intended thereby.

EXAMPLE 1

[0043] BCDMH powders having the particle size distribution disclosedherein are made using conventional methods. The powdered product isremoved from the reactor, and is dried using centrifuging and flashdrying.

[0044] The material is then increased in size using a roll compactor.Following compaction, the material is scalped using a 60 or 80 meshscreen to remove all material larger than desired. The material is thenpassed through a Turbo-Screener, Air Classifier, or other sizeclassification devices to remove fine material using a 200 mesh screenor equivalent separation.

[0045] The produced product consists essentially of BCDMH powder,particularly consisting of about 85% or more BCDMH and about 15% or lesssalt.

EXAMPLE 2

[0046] The rapid-dissolution property of the inventive BCDMH powderswere confirmed by measuring dissolution rates for the inventive andprior art BCDMH powders using the method described below at atemperature of about 25° C. The general goal for dissolution is toachieve a dissolution rate similar to that of currently available BCDMHpowders (e.g., BromiCide® powder from Bio-Lab, Inc.), while a morespecific goal is to produce a material, which dissolves at the 90% levelin no more than 5-10 minutes.

Method

[0047] 1. Flush a mixing tank with de-ionized water and fill to apredetermined level.

[0048] 2. Mix the water in the tank with a mixer set at 850 rpm. Use atank circulation system capable of turning the tank volume over at leastonce every 5 minutes.

[0049] 3. Determine and obtain the amount of sample needed and placeinto the water tank.

[0050] 4. Remove a sample of water with a large syringe and filter intoa disposable centrifuge tube.

[0051] 5. This process is performed for each of the timed intervals, asquickly as possible.

[0052] 6. Transfer the filtered water from the vial to the sample cell.Wash the cell a couple of times with this water before filling it to the10 ml mark.

[0053] 7. Clean the outside of the cell and place into the calorimeter.Press zero, then press read. The value 0.00 should be displayed bothtimes.

[0054] 8. Add one packet of DPD Total Chlorine to the cell, shake for 20seconds, and then let stand for three minutes before taking a reading.

[0055] 9. A blank must be run to assure the tank is free of anyhalogens. This is performed before any sample is added. An acceptableinitial value is between 0.00 and 0.03 mg/L Cl₂.

[0056] 10. The water temperature should remain around 23-26° C. Samplesshould be taken at frequent time intervals to insure that enough data isobtained to make a plot of the amount dissolved vs time.

[0057] 11. Plot the data and determine the maximum level of halogenobtained. Determine the time required for 90% of the material to go intosolution.

[0058] Calculations: (refer to Table 1 below)

[0059] Maximum Values: Current Invention=1.59 ppm

[0060] Powder XG=1.55 ppm

[0061] The dissolution concentration at 90% is around 1.44 ppm for thecurrent invention, and about 1.40 ppm for BromiCide® Powder XG. As canbe seen from the graphs shown in FIGS. 1 and 2, and from Table 1 below,both the inventive BCDMH powder and the current Powder XG dissolved tothe 90% level in less than 9 minutes. Table 2 below relates calculateddissolution times to the 90% level for samples of the current inventionand Powder XG at 25° C. TABLE 1 Dissolution data for products at 25° C.Halogen in ppm as Cl₂ (Minutes) Current Invention Powder XG 0.0 0.000.00 1 0.35 0.48 2 0.62 0.76 3 0.86 0.91 4 1.05 1.04 5 1.19 1.16 6 1.291.20 7 1.35 1.31 8 1.38 1.37 9 1.46 1.43 10 1.51 1.47 12.5 1.55 1.50 151.56 1.52 17.5 1.58 1.54 20 1.599 1.55 25 1.57 1.53 30 1.56 1.49 40 1.58— 50 1.55 — 60 1.57 —

[0062] TABLE 2 Calculated dissolution times for CURRENT INVENTION andPowder XG samples at 25° C. Dissolution Times (minutes) for 90% LevelCurrent Invention Powder XG 8.8 8.5 7.1 7.1 10.2 7.5 9.5 8.4 8.5 8.1 8.75.3 10.3 6.4

EXAMPLE 3

[0063] The rapid-dissolution property of the inventive BCDMH powderswere confirmed by measuring dissolution rates for the inventive andprior art BCDMH powders using the method described in Example 2, but ata temperature of about 35° C. The general goal for dissolution is toachieve a dissolution rate similar to that of currently available BCDMHpowders (e.g., BromiCide® powder from Bio-Lab, Inc.), while a morespecific goal is to produce a material, which dissolves at the 90% levelin no more than 5-10 minutes.

[0064] Calculations: (refer to Table 3 below)

[0065] Maximum Values: Current invention=1.61 ppm

[0066] Powder XG=1.50 ppm

[0067] The dissolution concentration at 90% is around 1.45 ppm forcurrent invention and 1.44 ppm for BromiCide® Powder XG. As can be seenfrom FIG. 3, FIG. 4, and Table 3 below, both the inventive BCDMH powderand the current Powder XG dissolved to the 90% level in about 5 minutes.Table 4 below relates calculated dissolution times to the 90% level forsamples of the current invention and Powder XG at 35° C. TABLE 3Dissolution data for products at 35° C. Halogen in ppm as Cl₂ CURRENTINVENTION (Inventive (Minutes) BCDMH Powder) Powder XG 0.0 0.01 0.00 10.63 0.78 2 0.78 0.99 3 0.89 1.08 4 1.29 1.20 5 1.44 1.34 6 1.53 1.38 71.61 1.49 8 1.57 1.51 9 1.60 1.51 10 1.62 1.49 12.5 1.59 1.47 15 1.571.53 17.5 1.64 1.50 20 1.62 1.49 25 1.58 — 30 1.61 —

[0068] TABLE 4 Calculated dissolution times for current invention andPowder XG samples at 35° C. Dissolution Times (minutes) for 90% LevelCURRENT INVENTION Powder XG 5.1 5.1 5.1 4.7 5.5 4.8 5.4 5.0 4.6 4.6 4.93.9 6.1 4.5

EXAMPLE 4

[0069] The “dusting” of the inventive BCDMR powders were tested using amethod from the CIPAC Handbook modified below (W. Dobrat and A. Martin,“MT171 Dusting of Granular Products,” CIPAC Handbook, Physico-chemicalMethods for Technical and Formulated Pesticides, Volume F, 1995,425-429).

Method:

[0070] 1. Clean crucible and place a filter in the bottom. Weigh to thenearest 0.001 gram to determine the tare weight. Be sure allfingerprints and foreign particle are removed from the crucible beforeweight is obtained.

[0071] 2. Place the crucible in the opening in the bottom box using theelastic bands to help seal the opening. Place the lid with the longcylinder tube on the box and screw down.

[0072] 3. Insert the stopper into the opening at the top of the tub.

[0073] 4. Obtain approximately a five gram sample and place on top ofthe stopper.

[0074] 5. Remove the stopper and allow one second to pass before thevacuum is activated and the 60 second timer is started. Make anyadjustments necessary to keep the pressure at 0.7 SCFM.

[0075] 6. When test is complete remove the lid and crucible. Carefullyclean any stray particle that may be lying on the inside or around theoutside of the crucible with kimwipes®.

[0076] 7. Weigh the crucible to obtain the gross weight. The percentdust is determined by the subtracting the tare weight from the grossweight and dividing by the sample weight and multiplying by 100 percent.

[0077] 8. The entire apparatus needs to be cleaned before the next testcan be run.

[0078] Calculations and Results

% Dust=((Gross weight−Tare weight)/sample weight)*100%

[0079] The following data in Table 5 tabulates % Dust values for bothPowder XG and the present invention. The inventive powders reduceddusting by more than 90%, and thus satisfied the stated requirements forreduced dusting. TABLE 5 % Dust Values for current invention and PowderXG. % Dust Values CURRENT INVENTION Powder XG 0.08 0.67 0.07 0.86 0.170.79 0.03 0.86 0.05 0.82 0.08 0.81 0.08 0.71

EXAMPLE 5

[0080] The flow characteristics of the inventive BCDMH powders wereinvestigated by testing the powder under the conditions that would beexperienced in a paper making plant. The inventive powders had superiorflow when compared to prior art powders. Comparisons of flow were madeby feeding the material with a typical powder feeder device used in thefield at a paper making plant. Measurement ranges were determined forthe amount of material dispensed for one (1) revolution of the feedingscrew. Table 6 below compares data obtained from the current invention,Powder XG, and Lonza's BCDMH Powder. TABLE 6 Feed Rate data for varioussamples. Feed Rate Product (grams/revolution) Current Invention 110-120Powder XG  90-100 Lonza Material 69-75

EXAMPLE 6

[0081] The density of the inventive BCDMH powders were evaluated bymaking measurements of bulk density and tap density using the methoddescribed below.

Bulk Density Method

[0082] 1. Determine the tare weight (g) of a 100 ml graduated cylinder.

[0083] 2. Add BCDMH material to the 100 ml line and determine the grossweight (g) of the cylinder and the sample.

[0084] 3. Determine the bulk density in grams/L by using the formula:

Bulk Density=(Gross Weight (g)−Tare Weight (g))/(0.100 L)

Tap Density Method:

[0085] 1. Take the sample of material and graduated cylinder from theBulk Density Test above.

[0086] 2. Gently tap the bottom of the cylinder on the counter tocompact the material.

[0087] 3. Tap a total of 50 times. Record the final volume of thematerial in L.

[0088] 4. Determine the tap density in grams/L by using the formula:

Tap Density=(Gross Weight (g)−Tare Weight (g)) /(Final Volume (L))

[0089] The data in table 7 below compares the bulk density and tapdensity from the current invention and Powder XG. The data indicatesthat the current invention has a much higher bulk density indicating amuch more compact material. The data also indicates that the Powder XGmay compact some, but will not have near the same tap density as thecurrent invention. TABLE 7 Bulk density and Tap density measurements forcurrent invention and Powder XG. Current Invention Powder XG BulkDensity Tap Density Bulk Density Tap Density (Grams/L) (Grams/L)(Grams/L) (Grams/L) 879.5 993.8 660.2 835.7 874.7 994.0 657.9 812.2882.0 991.0 662.1 817.4

EXAMPLE 7

[0090] The wetability of the current invention and powder XG wasmeasured in the laboratory and observed at an on-site application duringa recent field trial. The laboratory method is described below.

[0091] 1. Fill a 1000 ml beaker with 500 ml deionized water.

[0092] 2. Add 10 grams of sample to the top of the water.

[0093] 3. Gently mix to simulate mixing tank.

[0094] 4. Determine the time necessary for the material to settle to thebottom of the beaker.

[0095] Table 8 below shows wetability data for the current invention andPowder XG. A specific observation that was made during the test statedthat a portion of the Powder XG material agglomerated on the surfaceinto chucks and settled to the bottom of the beaker. These agglomerateswere not wetted properly and remanded as agglomerates on the bottom ofthe beaker throughout the remainder of the test. The time that wasrecorded was the time that the bulk of the material settled to thebottom of the cylinder. This test shows the superior wetabilitycharacteristics of the current invention. TABLE 8 Wetability Data inminutes for current invention and Powder XG. Wetability Data for CurrentInvention and Powder XG (minutes) Current Invention Powder XG 8minutes >13 minutes

[0096] A field application was performed with the current invention toprove product usability. Several pictures were taken of the mixingchamber to show wetting properties and are shown in FIGS. 5, 6, and 7.FIG. 5 shows the current invention as it is added to the mixing chamber.It is apparent that there is little or no material floating on thesurface with minimal frothing/foaming. The pictures related in FIGS. 6and 7 show Powder XG and a competitor's product. In both pictures, thereis a considerable amount of frothing and material floating on thesurface of the mixing chamber. This floating material is an example ofan inconsistent mix due to poor wetting properties.

[0097] While the invention has been illustrated and described in detailin the drawings and foregoing description, the same is to be consideredas illustrative and not restrictive in character, it being understoodthat only the preferred embodiment has been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected.

We claim:
 1. A powdered halogenated hydantoin product consistingessentially of: (a) 70-100% halogenated hydantoin particles sizedbetween 80 mesh and 200 mesh; (b) 0-20% halogenated hydantoin particlessized larger than 80 mesh; and (c) 0-10% halogenated hydantoin particlessized smaller than 200 mesh.
 2. The powdered halogenated hydantoinproduct of claim 1 wherein the powdered halogenated hydantoin productconsists essentially of: (a) 90-100% halogenated hydantoin particlessized between 60 mesh and 200 mesh; (b) 0-5% halogenated hydantoinparticles sized larger than 60 mesh; and (c) 0-5% halogenated hydantoinparticles sized smaller than 200 mesh.
 3. The powdered halogenatedhydantoin product of claim 1 wherein the powdered halogenated hydantoinis bromochlorodimethylhydantoin.
 4. The powdered halogenated hydantoinproduct of claim 2 wherein the powdered halogenated hydantoin isbromochlorodimethylhydantoin.
 5. A method of treating water, said methodcomprising adding to the water a water treatment composition comprisingpowdered halogenated hydantoin; wherein said halogenated hydantoinconsists essentially of: (a) 70-100% halogenated hydantoin particlessized between 80 mesh and 200 mesh; (b) 0-20% halogenated hydantoinparticles sized larger than 80 mesh; and (c) 0-10% halogenated hydantoinparticles sized smaller than 200 mesh.
 6. The method of claim 5 whereinsaid powdered halogenated hydantoin product consists essentially of: (a)90-100% halogenated hydantoin particles sized between 60 mesh and 200mesh; (b) 0-5% halogenated hydantoin particles sized larger than 60mesh; and (c) 0-5% halogenated hydantoin particles sized smaller than200 mesh.
 7. The method of claim 5 wherein the powdered halogenatedhydantoin is bromochlorodimethylhydantoin.
 8. The method of claim 6wherein the powdered halogenated hydantoin isbromochlorodimethylhydantoin.